Insulator with nested parts



Sept. 15, 1931. A. o. AUSTIN INSULATOR WITH NESTED PARTS Filed May 25, 1925 Fly] 16 INVENTOR.

B? M a M I ATTORNEYJ' Patented Sept. 15, 1931 UNITED STATES PATENT OFFICE ARTHUR O. AUSTIN, OF BARBERTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE OHIO BRASS COMPANY, OF MANSFIELD, OHIO, A CORPORATION OF NEW JERSEY INSULATOR WITH NESTED PARTS Application filed May 25,

This invention relates to insulators having a plurality of parts made of fragile material such as porcelain, nested together, and has for its object the provision of such insulators which are of improved construction and operation and in which the danger of mechanical failure of the insulator as a whole, in case of injury to one of the parts,

is reduced to a minimum. The invention an is exemplified in the combination and arrangement of parts shown in the accompanying drawings and described in the following specification and it is more particularly pointed out in the appended claims.

In the drawings:

Fig. 1 is an elevation with parts in section showing one embodiment of the present invention.

Fig. 2 is a fragmentary horizontal sectional view of the insulator shown in Fig. 1

on a plane just below the lower side of the cap 14.

In insulators having a number of nested parts, the cemented surfaces of the inner :15 parts are not only smaller providing less gripping area, but there is frequently little or no overlap between the outermost parts and the innermost parts. In many cases this is of serious consequence, for if the ".o fragile dielectric comprising the parts should crack, it is possible for the insulator to come apart.

One common type of construction upon which it is desired to insure the highest dezis gree of mechanical reliability is that class of multipart insulators used for bus and switch work. Fig. 1 shows an insulator of this class, although the principle may apply equally well to multipart suspension insulaio tors and pin type insulators in general. In Fig. 1 the dielectric shells 10, 11, 12 and 13 are cemented to a metal cap 14 and a metal pin 15 having mounting base 16. The cap 14 is cemented to the dielectric shell 10. The

' 15 area for gripping along the sides of the shell 1925. Serial No. 32,714.

dielectric member 13. Since the dielectric members are of fragile material, it is possible that a crack through the several members may permit the mechanical separation between the pin 15 and the cap 14. Thermal stresses or mechanical stresses set up by the load or unusual stresses set up by fire or water might easily cause the cracking of the porcelain members in such a way that the two metal parts could fall apart. This might permit the line or bus structure to come down and cause considerable damage or loss of life. It is evident that if the metal pin 15 had the dimensions of the dielectric member 11 and was cemented into the dielectric member 10 that it would be practically impossible to separate the two metal pieces mechanically unless the dielectric or cement was almost completely destroyed.

Where a number of insulator parts are nested together, in order to insure mechanical reliability against failure due to cracl ing of the porcelain, it is practically necessary to provide a reasonable amount of grip surface of an outer member on the member enclosed thereby above a line drawn inwardly and upwardly at to the axis of the insulator from the lowest supported point on the outer face of the outer member. This is because of the fact that the direction of the resultant stresses in the dielectric is at an angle of approximately 45 to the axis of the insulator. It follows from this that, to be effective, reinforcing members between the nested parts should overlap by an amount of at least as great as the distance by which the parts are separated.

It is evident that in order for the two metal fittings of an insulator to overlap the nesting of the insulator parts must be very considerable in large insulators. This increases the area under electrical stress, greatly increases the cost and difficulty of manufacture and, in addition, the stresses set up due to changes in temperature or differential expansion between the metal parts and the porcelain may tend to cause the parts to fail electrically.

The present invention eliminates the difficulty of manufacture, permits a material increase, in mechanical strength in some cases and also provides the necessary overlap between metallic parts so that the insulator cannot come apart with the cracking of the dielectric under operating conditions.

In order to produce the desired result, suitable metallic members are placed in the joints. One of these members 18 is shown embedded in the cement oint between dielec-' tric members 10 and 11. In this particular case the metallic member is made of thin metal having roughened or grooved walls and a closed end. The member is shown in section in Fig. 2. It will be seen that the member 18 is waved or deformed so teat it will grip the cement in all directions providing gripping means between the metallic members for torsion or for bending moment. This metallic member is inserted in the when the parts are assembled together or it may be assembled to one part in advance of the other. edge of this member projects below the lower edge of metallic member 14-. This makes it easier to provide an overlap for the head of dielectric member 12. A metallic member 19 is placed in the joint between dielectric members 11 and 12. These metallic members may be made in the form of ings, pressed metal, in the form of wire screen or any member which has the necessary mechanical properties for holding the parts together and, at the same time, providing a suitable grip between the parts. One form is shown in 20. This member is simply in the form of a cylinder having a number of holes or windows. In this case practically a smooth cylinder may be used as the gripping is formed through the cement in the windows or openings. In this type it is possible to relieve any mechanical stress which might otherwise be set up by the expansion of the metal as the metal member is coated with wax or other yielding material, without affecting the tightness of the joint.

The metallic inserts in the joints not only provide reinforcements to prevent mechanical failure but tend to insure a proper distribution of electrostatic stress which otherwise is frequently changed by increased resistanceof the cement. due to drying.

It will .be noted that the cement surface in contact with the metallic inserts increases with the diameter of the various nestedparts. The member 18 in Fig. 1 has a larger surface area in contact with the cement than does the member 19 and the member 19 in turn has a larger surface area than the mem ber 20. For this reason, it is sufficient merely to'undulate the surfaceof the member 18 while the member 20 is provided with perforations which receive the cement, thus giving a firmer hold on the insertand' compensating It will be seen that the lower.

forthe smaller surface contact. The netting 19 in the intermediate joint, while not provided with the large perforations of the member 20 gives a firmer engagement with the cement for the given area than does the unperforated member 18.

V I claim:

1. An insulator comprising a plurality of dielectric membe *s nested together and forming overlappingjoints therebetween, metallic fittings secured to the outermost ones of said members and overlapping metallic members disposed in said joints, one of said reinforcing members consisting of a sheet metal cup having walls thereof extending into the joints between two of said dielectric members while another of said reinforcing members consists of a sheet metal ring disposed in the joint between two of said dielectric members, said ring being disposed Within said cup.

2. An insulator comprising a plurality of nested dielectric members connected by cement interposed between said members and sheet metal, reinforcing members disposed in the joints outer reinforcing member being formed of imperforate sheet metal having the surface thereof undulated wln'le an inner reinforcing member is formed of sheet metal having perforations therethrough to permit connecting ties of cement to extend through said inner reinforcing member.

In testimony whereof I have signed my name to this specification on this 21st day of an A. D. 1925.

ARTHUR o. AUSTIN.

formed b said cement an. 

